1. Field of the Invention
The present invention relates to powered lawn edgers. In particular, the present invention relates to a safe, compact, streamlined, and extremely maneuverable powered lawn edger which is steerable with both hands in the manner of a wheelbarrow.
2. Description of the Prior Art
Hitherto, powered lawn edgers have been able to be divided into several categories. The first is a multi-wheeled carriage which is self-supporting on its wheels and which is pushed along its intended path. The best known member of this class is essentially a conventional domestic lawn mower type but with a cutting element rotating in a vertical plane. Another category is a hand held device which does not normally have any ground engaging wheels and which is carried by the operator. The best known of these devices are the various types of brush cutter or trimming devices.
The brush cutter type of device generally includes a nylon filament as a cutting element. This cutting element is attached to a cutter head which is set at one (lower) end of a long drive shaft. The drive shaft is supported by the operator at an angle of approximately 45.degree. to the horizontal. The shaft has an engine at its other (upper) end with the engine mostly situated behind the operator and in some other cases besides the operator. The cutter head rotates about a substantially horizontal plane in normal use and is intended, for example, to trim grass growing adjacent tree trunks, to mow grass in small and/or awkward areas, and the like. Therefore, in order to trim the edge of a lawn adjacent a footpath, for example, it is necessary for such an apparatus to be completely carried while being twisted by approximately 90.degree. about its longitudinal axis in order to bring the plane in which the cutting device rotates into an inclined, but nearly vertical, position. This places the complete apparatus in an extremely out of balance position, and this particularly awkward motion requires an awkward operator position. Also, a particularly awkward crab-like walking motion is required during use. Indeed, most operators walk backwards and sideways simultaneously. Therefore, it is both difficult and tiring to execute.
As a consequence, any health problem of the operator, such as common backache, can be exacerbated by this stooped and unnatural position. The tiredness of the operator is further increased by the need to actually carry, and therefore support the entire weight of, the device during its operation. Furthermore, unlike a blade of a lawn edger, the nylon filament of such trimming devices does not cut into the soil surface and therefore does not give a clean cut or neat edge.
Other prior art variations include lawn edge cutting attachments for such brush cutter devices. These include those in which the rotatable implement rotates in a substantially vertical plane. Typically, these devices use a short, high peripheral speed, cutter blade which penetrates the soil surface to edge the lawn. However, these devices, with the engine behind or beside the operator, still suffer from the fundamental disadvantage that the entire weight of the apparatus is carried by the operator at an angle of about 45 degrees away from the cutter blade axis. Furthermore, to make the cutter blade penetrate the soil surface, the operator has to stoop further in order to force the entire cutting head downwardly.
These prior art brush cutter type devices also only have a safety guard parallel to (and positioned above) the cutting head for protection during normal grass cutting when the head is cutting horizontally. As a result, when the apparatus is maneuvered so that the cutting head is rotating in a near vertical plane for lawn edging, then this exposes the cutting head and allows any hidden object, such as stones, sand or even foreign objects such as nails from previous building debris, etc., to be thrown up out of the grass at speed. Of course, such objects then become high speed projectiles which are dangerous to both operator and bystanders, be they distant or close by.
It is also known for some such prior art brush cutter devices to be fitted with a small roller attached to the device near the cutter head. These devices still have their engine alongside, or behind, the operator, so the majority of the weight is still supported by the operator with the same generally awkward stance and movement as described above. One hand of the operator carries the majority of weight while the other hand of the operator holds down, or forces down, the cutter head. Again this causes stooping which exacerbates any back problem. Back problems are a major source of health insurance injury claims and are a major source of injury for manual labourers.
Various prior art devices in the form of a wheeled dolly have been proposed in order to support such brushcutter devices. The following U.S. patents are typical of such devices: U.S. Pat. No. 4,182,100 (Letter); U.S. Pat. No. 4,442,659 (Enbusk); U.S. Pat. No. 4,531,350 (Huthmacher); U.S. Pat. No. 4,803,831 (Carmine); U.S. Pat. No. 4,879,869 (Buckendorf, Jr.); U.S. Pat. No. 4,894,916 (Nimz et al.); U.S. Pat. No. 4,922,694 (Emoto); U.S. Pat. No. 4,936,886 (Quillen); U.S. Pat. No. 5,029,435 (Buchanan); and U.S. Pat. No. 5,095,687 (Andrew et al.).
Similarly, two U.S. Pat. Nos. 4,364,435 and Re.32,266, both to Tuggle et al., disclose a single, small diameter, roller support for a brushcutter device; and an earlier U.S. Pat. No. 4,286,675 to Tuggle discloses a single wheel support for a brushcutter. In these three patents, the weight of the engine of the brushcutter is supported by a handle connected to that engine, while an outrigger handle is provided for stability. Again, because the heaviest component of the device, namely the engine, is directly supported by a handle held by the operator, the operator awkwardly supports most of the weight of the device with one bent arm. The other arm is outstretched and holds the outrigger handle.
A further problem to be considered is the expected restrictions to be placed on small two-stroke (two-cycle) engines because of the pollution such engines create over and above that created by four-stroke engines. As a consequence, the lightweight two-stroke power units currently used in brushcutters and similar devices are likely to be banned in some jurisdictions in the future for anti-pollution reasons. The engineering result of this is that commercially acceptable power units are henceforth likely to be restricted to four-stroke internal combustion engines and electric motors, both of which are substantially heavier than two-stroke engines. It follows, therefore, that in the future those brush cutters in which the operator carries the weight of the apparatus will become eventually impractical.
The wheeled carriage class of prior art lawn edger typically has three (or sometimes four) wheels arranged so as to enable the edger to be free standing, with upstanding handles, and also self-supporting on its wheels. These wheels hold the device so that the rotatable cutters rotate in a substantially vertical plane. The device is pushed in a manner analogous to that of a lawn mower. Because these self-supporting three and four wheeled carriage grass edgers have a long wheel base to self-support the apparatus, when pushed (forward), their natural track is straight; and, therefore, to edge around a curve is very difficult, with the operator having to "bounce," or reciprocate, or drag, the apparatus around, to try to approximate to the curve which the non-steerable carriage wheels will not follow. Also, the weight of these prior art devices is distributed amongst the three or four carriage wheels so the cutter blade does not have a great deal of weight (downwardly direct force) applied to it. This is due to the long leverage distance between the cutter blade axis and the rear wheels (which constitute the pivot point when reaction forces are applied to the blade when the blade strikes hard ground). As a consequence, the blade pushes the front of the machine upwardly when the blade strikes hard ground. As a result, in hard soils this weight distribution and reaction force can cause the carriage to "bounce" and be less stable.
In addition, because of the wide side to side spacing between the wheels of the free standing carriage, necessary to make the carriage stable, it is difficult to tilt the edger so as to move the cutting blade out of the vertical plane in which it rotates. Typical of these prior art devices are those disclosed in the following U.S. Pat. No. 2,847,813 (Hanson, Jr., et al.); U.S. Pat. No. 3,130,793 (Allegretti); and U.S. Pat. No. 3,734,196 (Mangum).
For a prior art edger having a three (or four) wheeled carriage, it is possible for the edger to be tilted sideways in one direction. This is the direction in which the wheel(s) furthest from the cutter is lifted. This tilts the lower edge of the "disc" in which the blades rotate towards the lifted wheel. This is generally non-effective since the movement of the "disc" in which the blades rotate is towards the wheels. In order to tilt the "disc" in the other direction., it is necessary to raise the engine, and so the cutter blade is raised upwardly, away and well clear from the ground surface. This is caused by the spacing between the cutter blade and the remaining ground engaging wheel(s). The raised "disc" means that the cutter blade(s) do not come into contact with the material to be cut. U.S. Pat. No. 2,847,813 (Hanson, Jr., et al.); U.S. Pat. No. 3,130,793 (Allegretti) and U.S. Pat. No. 3,734,196 (Mangum); and "WEEDEATER" (Registered Trade Mark) gasoline model GE21 as sold by "ELECTROLUX" exemplify this art. This inability to operatively tilt the device creates substantial problems, particularly in edging against walls and fences and also in edging adjacent curbs and gutters.
In order to overcome this problem, it is known to provide some models of such wheeled carriage edgers, and these can be categorized as heavy duty edgers, with a swivel mechanism to enable the cutting blade(s) to be tilted out of the vertical plane. Generally such swivel mechanisms take the form of a tiltable axis of rotation of the cutter, and a V-belt drive which is able to accommodate the necessary twisting required while still transmitting power. The power unit remains untilted. While such arrangements are functional, the devices are heavier, more complicated and more expensive. In addition, the (often exposed) V-belt drives are dangerous.
Such prior art heavy duty edgers also require the operator to pull or push a locking device, and/or twist or pull or push a lever, so that the plane of the cutter is tilted and locked at its desired position. This is an operation that is not fast or simple, and for old or less athletic operators in domestic situations can be difficult to execute. These belt drive edgers also are provided with an adjustment mechanism to tension the belt drive. Thus, the motor and cutter blade shaft are not at a fixed distance from each other.
Examples of prior art wheeled carriage devices which have attempted to deal with this problem include U.S. Pat. No. 2,680,945 (Reed); U.S. Pat. No. 2,791,875 (Faas); U.S. Pat. No. 2,855,742 (Cooper et al.); U.S. Pat. No. 2,930,176 (Lindell); U.S. Pat. No. 3,090,186 (Dykes et al.); U.S. Pat. No. 3,193,996 (Wellborn); U.S. Pat. No. 3,490,213 (Pinto); U.S. Pat. No. 3,743,028 (McCloud); U.S. Pat. No. 4,962,631 (Braun et al.); U.S. Pat. No. 5,156,217 (Hirata et al.); and U.S. Pat. No. 5,165,485 (Fujikawa et al.). The commercially available "MASPORT" (Registered Trade Mark) model 6002 DLX also has a blade tilting arrangement. All of these "heavy duty" wheeled edgers are heavy and bulky, difficult to transport, cannot fit into a boot or trunk of even a large car, and require a great deal of room for storage.
Another example of a prior art device in which the cutting blades are able to be tilted out of the vertical plane is provided by U.S. Pat. No. 2,970,419 (Lieberman). This device enables a cut to be achieved both in a horizontal plane and in a vertical plane. When cutting in a horizontal plane, the device is supported by a pair of wheels 40 and when cutting in a vertical plane, the device is supported by a roller 54. U.S. Pat. No. 2,672,002 (Nelson) discloses a somewhat similar device which, when cutting in the vertical plane, is supported by single wheel 15 in front of the cutter blade, but when cutting in the horizontal plane, is supported by a skid bar 28. Because of the skid bar 28, it is necessary to "shove or push" the device in the direction of the bar 28 utilizing a handle 31 which has "any desirable crosshead" and, therefore, is substantially T-shaped in configuration.
U.S. Pat. No. 2,621,463 (Skillman) discloses a similar arrangement in which the device is supported in both cutting actions by a roller 11 having a substantial axial extent. Again, the cutting blades are able to be pivoted so as to cut in either a horizontal plane or a vertical plane. U.S. Pat. No. 2,632,990 (Stricklen et al.) discloses a single-wheeled carriage device with a free standing and upstanding handle. The carriage has supporting shoes or skids 20 to maintain the carriage upright in the rest position. The device is able to cut either vertically or horizontally. When cutting horizontally, the cutter blade is able to be pivoted in a horizontal plane about a vertical axis on a cutter support arm. When cutting vertically, the line of cut is substantially offset from the center line of the machine. A complex belt drive is required.
U.S. Pat. No. 2,618,919 (Hutchens) also discloses a single-wheeled carriage arrangement with both a horizontally cutting trimmer blade 11 and a vertically cutting cutter blade 19. Each of these blades is able to be swivelled to a tilted position and independently operated so that simultaneous inclined cuts, or two simultaneous horizontal cuts, are able to be achieved. This device is supported by a single wheel and a pair of short legs 31. The device has a conventional free standing and upstanding handle 29 which is presumed to be the then conventional T-shaped lawnmower handle. Each cutting blade, in order to swivel, is mounted on an outrigger journal and is at a considerable horizontal distance from the wheel when the blade is in the vertical position. Except for the handle arrangement, the device is of very broad dimensions with the cutters extending a long way forward of the single wheel. This single wheel is placed approximately midway front to rear and approximately on the center line of this carriage device to constitute both a front to rear and a left to right pivot point. However, the carriage has substantial masses located at some distance from the pivot or balance point. As a result, the device is unwieldly, being difficult to balance and therefore difficult to use.
In a follow-up invention, the same inventor in U.S. Pat. No. 2,719,398 discloses basically the same machine as previously but with only a single cutter rotating in a swivel titled position or a vertical plane. Again, the cutter is mounted on a swivel outrigger journal which, when the blade is vertically aligned, is spaced sideways by a substantial horizontal distance from the wheel. This swivel arrangement of the cutter is necessary to enable any effective titled cut to be achieved, as the wide dimensions and low clearance of the frame of the carriage device prevent laterally tilted cutting action. As before with his earlier device, tilted cuts can only be achieved by swivelling the outrigger arm of the blade. For this reason a separate cutter blade tilt mechanism is provided to enable effective edging with the tilted blade, for example for edging against a wall. This single wheel device is again pushed by a conventional free standing and upstanding single shaft mower-type handle 20 which is again presumed to have a T-shaped upper end as was then conventional.
U.S. Pat. No. 2,478,813 (Esleck) also discloses a single wheel carriage device with a conventional free standing and upstanding T-shaped handle 7 with a pair of closely spaced hand grips 17. In this lawn edger the axes of the single supporting wheel 14 and the cutter blade 29 are aligned or coincident. Similarly, U.S. Pat. No. 2,707,859 (Walker) also discloses a device having a vertical cutting disc supported by a single wheel 12 and manipulated by a conventional handle 14 having a cross head handle 15 with two closely spaced handgrips. The wheel 12 is in front of the cutter.
U.S. Pat. No. 2,708,335 (Newton) also discloses a single wheel device which in this instance is able to cut both horizontally and vertically. The single wheel supports the motor and cutter blade while cutting vertically. It is not clear how the device is supported during horizontal cutting as illustrated in FIG. 5. In this device the handle 27 consists of a single bent tube and, therefore, it would be necessary for the operator to keep a very firm grip on the handle in order to prevent the device from twisting or tilting while cutting vertically. U.S. Pat. No. 2,653,381 (Rooke) discloses a similar device with a rod-like handle 27 which again has a single grip 43. A roller 36 supports the device while trimming vertically, and the device appears to be supported by skids while cutting horizontally.
U.S. Pat. No. 4,033,098 (Green) discloses a device for cutting horizontally which has a single wheel 11 and a pair of spaced apart handles 33. As seen in FIG. 5, in order to cut grass adjacent a wall 42, it is necessary for the handles 33 to be released, then twisted to one side and then secured in that position in order that the operator's hand not be scraped during the passage along the wall 42. Furthermore, because the large motor 12 is mounted forwardly of the wheel 11, the center of gravity of the device is forward of the wheel 11. Therefore, in operation it is necessary for the handles 33 to be forced downwardly in order to maintain the correct cutting height. If, during operation, the handles 33 are inadvertently released, then the cutting elements 28 immediately impact with the ground, which is extremely dangerous.
Another single-wheeled device in which the center of gravity is forward of the single wheel is that disclosed in Australian Patent No. 107,917 (Collins and Henderson). This device has a cutting disc 4 which normally rotates in a horizontal plane above a pair of skids 16 which assist to support the weight of the device. The weight of the cutting arrangement means that the center of gravity of the device is forward of the wheel 2, notwithstanding that the engine 3 is mounted above, but just behind, the wheel 2. Again, in operation it is necessary for the operator to push down on the handles 13 in order to relieve the weight on the skids 16.
U.S. Pat. No. 4,845,929 (Kawasaki et al.) again discloses a device for cutting horizontally (rather than vertical edging) in which a pair of wheels is positioned inside a dome-shaped cutting disc. The wheels are pivotable about a vertical axis in order to permit cutting in different directions. In the second embodiment of FIGS. 19-23, the trimmer is supported by a pair of running wheels 8, and a skid 170 (column 12, line 37) but designated 156 in FIG. 20. This indicates that the center of gravity of the device is forward of the wheels 8 and, therefore, the guide handles 16 have to be depressed in order to operate the device.
U.S. Pat. No. 3,168,147 (Peters) discloses a single wheel carriage device with free standing and upstanding handles. The offset handles enable the operator to overcome the tendency of the out of balance device to tip laterally. The cutter blade 11 is on an outrigger journal which is offset to one side. The foot 24 stops both lateral tilting and rearward tilting. The apparatus is unstable and difficult to use, especially considering the awkward situation of the operator. This is because of the geometry of the apparatus including the considerable horizontal distance between the wheel center line and the cutter blade. Thus, it is impractical to try to laterally tilt the apparatus for a tilted cut. Further, the operator is required to simultaneously push and hold forward (against spring pressure) the pad 16. This holds down the pivoted journal arm for the blade, to set the blade's cutting position. As well as having to overcome the spring pressure, the operator also has to have enough thumb strength to stop the blade "bouncing" out of the ground. This applies particularly if the ground is hard, or worse still, if the blade hits a solid object.
U.S. Pat. No. 3,533,223 (Gunn et al.) discloses a sand trap edger with floatable blade carrying arm supported by a second wheel. The cutter blade is a substantial horizontal distance from the wheel center line and mounted in an outrigger fashion. U.S. Pat. No. 2,706,941 (Swanson) discloses a single-wheel device but has the wheel forward of the cutter. The operator is said to walk backwards with base plate 10 sliding over the grass surface.
A further problem to be considered is the present and future mandatory safety requirements in some jurisdictions whereby it is, or will be, required that the blade of the lawn edger must come to a complete stop within a given time after the operator releases the engine throttle. This is similar to the present regulations applying to rotary lawn mowers in these jurisdictions. The specified amount of time varies from one jurisdiction to another but is typically as short a time as three seconds.
U.S. Pat. No. 4,984,417 (Braun et al.) is an example of a (belt driven) lawn edger with a safety brake arrangement fitted.
As a consequence of this regulatory environment, lawn edgers which include this type of safety requirement of stopping or braking the blade within a given time will have an additional cost in the cost of manufacturing such edgers.
Such edgers, especially those with belt drives, normally have a four-stroke engine with an output shaft speed in the vicinity of 1500-2000 rpm, which is approximately the same rotational speed desired for the cutter blade. As a consequence, the gear ratio of the belt drive is typically in the range of from 1:1 to 1.25:1 and almost never exceeds 1.5:1.
The consequence of this gear ratio is that when the clutch mechanism is disengaged (whether there be a centrifugal clutch or a declutching brought about by loosening of the belt tension), the cutter blade can continue to rotate for a substantial time. This is because the only mechanism which operates to slow the cutter blade is either the inertia of the clutch part or the friction of the loosened belt. For this reason a separate brake arrangement is necessary if safe operation and compliance with short stopping times are to be achieved.
It is the object of the present invention to substantially overcome or ameliorate some of the above-mentioned disadvantages and problems by the provision of a powered lawn edger which is steerable with both hands, able to be maneuvered in substantially the same fashion as a wheelbarrow, and able to be operated without tiring the operator. Therefore, the edger has a negligible turning circle, is able to be tilted easily to either side, and yet supports a substantial part of the weight of the powered device. In addition, the arrangement should enable weight (or downward force) to be concentrated at the cutter blade so as to improve stability.
In accordance with a first aspect of the present invention there is disclosed a powered lawn edger steerable by an operator with both hands in the manner of a wheelbarrow, said edger comprising:
an elongate frame having handle means adjacent one end thereof and a ground engaging wheel means having an axis of rotation adjacent the other end, said frame having a longitudinal axis; PA1 a power unit located in front of the operator and carried by said frame intermediate said ground engaging wheel means and said handle means; PA1 an enclosed power train interconnecting said power unit and a rotatable cutting device to rotate said rotatable cutting device, said rotatable cutting device being mounted for rotation in a substantially vertical plane in use, and being mounted adjacent said other end of said frame with its axis of rotation forward of said ground engaging wheel means axis of rotation; PA1 said handle means comprising a pair of spaced apart handlegrips; PA1 said edger having a center of gravity which, in use, lies in a substantially vertical plane passing through said ground engaging wheel means, and said center of gravity also being intermediate said handle means and said ground engaging wheel means, whereby said handlegrips can be manipulated to twist said frame about its longitudinal axis to laterally tilt said cutting device from said vertical plane of rotation. PA1 energizing said power unit to rotate said cutting device; PA1 holding said handlegrips one in each of a corresponding hand, walking along said path or roadway while wheeling said ground engaging wheel means thereover; PA1 steering said edger as necessary to align, or maintain aligned, said rotating cutter blade with the desired line of cut; and PA1 twisting said edger about the longitudinal axis of said elongate frame by adjusting the height of said handlegrips relative to said formed edge as necessary to adjust the desired angle of cut.
In accordance with a second aspect of the present invention there is disclosed in a powered lawn edger having a frame, at least one ground engaging wheel means supporting the frame, a power unit carried by the frame, a cutting device rotatable by said power unit, and height adjustment means to adjust the height of said cutting device relative to the ground, the improvement comprising a debris deflector carried with said wheel means, the height of said debris deflector relative to the ground being unchanged with operation of said height adjustment means.
In accordance with a third aspect of the present invention there is disclosed in a powered lawn edger having a frame, at least one ground engaging wheel means supporting said frame, a power unit carried by said frame, a throttle means to increase or decrease the speed of operation of said power unit, and a cutting device rotatable by said power unit, the improvement comprising a throttle interlock mechanism wherein said throttle is operable to increase the speed of said power unit above an idle speed only on immediately prior operation of said interlock mechanism.
In accordance with a fourth aspect of the present invention there is disclosed in a powered lawn edger having a frame, at least one ground engaging wheel means supporting the frame, a power unit carried by the frame, a cutting device rotatable by said power unit, and a transmission interconnecting said power unit and cutting device, the improvement comprising a gear reduction means included in said transmission and having a gear ratio in the range of from 1.5:1 to 8:1.
In accordance with a fifth aspect of the present invention there is disclosed a method of edging a lawn alongside a formed edge of a path or roadway utilizing the edger of the first aspect, said method comprising the steps of: